To our knowledge, this is the first study performed in Latin Europe regarding the genetic associations of heroin dependence. The study was aimed to examine the association of heroin dependence with the DRD2 TaqI A polymorphism in Spanish subjects of European origin. According with our results, the A1-A1 genotype of the DRD2 TaqI A polymorphism is associated with heroin dependence regardless of gender, while the A1 allele is associated with heroin dependence only in males. These results must be considered taking into account two aspects of the participant selection. First, heroin-dependent patients who participated in the present study were not excluded if they reported non-opioid substance use. Second, the most of cases and controls were males.
